In order to improve device-assembly property of electrical apparatus, its conductor is divided into several pieces. Therefore, a contact device for connecting between conductors to each other becomes necessary for easily assembling these conductors. In the contact device, because electric current also flows therethrough similarly to the conductors, in order to prevent heat generation due to electrical resistance, a stable low-electrical-resistance device is required. Moreover, based on a case-by-case system to which the device is applied, the device is required to have a function which absorbs a relative displacement due to size tolerance of the apparatus and/or that generated by thermal expansion/contraction of the conductors depending on its atmospheric condition.
For example, a conventional contact device of a gas-insulated switching apparatus has been configured in such a way that a pair of conductors arranged on the same axis are fitted to each other at their ends in the axis direction, and the conductive contact is arranged in a fitted portion between the conductors, so as to flow current therethrough (for example, refer to Patent Document 1).
The above described contact device disclosed in Patent Document 1 includes at least two kinds of gaps in the fitted portion of the conductor pair, and the gaps are formed by protrusions provided in a cylindrical inner periphery of the conductors. The contact device arranged in the fitted portion of the conductor pair is configured of a coil-spring shaped one having a spring action. A stable contact resistance to the conductor pair can be obtained by a contact load obtained by the spring action. According to such a configuration, in a contact portion of the conductor pair, because a stable contact load can be obtained even though varying the insertion angle of the conductors, a value of stable contact resistance can be obtained.
The spring contact is formed by spirally winding a bare wire constituted by highly electrical-conductive spring material with the wound wire being tilted by an angle less than 90 degrees to its winding axis, so as to be integral and belt-like, and is formed to be circular by jointing its both ends together, which is arranged in a groove provided along the circumferential direction on one of the fitted faces of the conductor pair. Here, the groove is provided in plural numbers along the axis direction, and a plurality of circular spring contacts is arranged in the axis direction.
Because the spring contact is formed by the spiral winding with tilting by the angle less than 90 degrees to the winding axis, its cross section perpendicular to the winding axis becomes elliptical, thereby providing a characteristic in which spring elasticity is provided thereon in the short-axis direction. Thereby, when the spring contact whose cross section is elliptical is fitted into the groove, with the side faces of the spring contact in the short axis direction facing the bottom face of the groove, and arranged in a gap between the pair conductors, elastic repulsion force of the spring contact acts between the spring contact and each of the conductors, providing a low-contact-resistance.
[Patent document 1]
    Japanese Patent Application Publication Laid-Open No. 2005-176536